浅埋软岩隧道围岩变形规律和支护受力特性研究

发布时间：2018-03-11 06:30

本文选题：浅埋软岩　切入点：现场试验　出处：《北京交通大学》2014年硕士论文　论文类型：学位论文

【摘要】：大规模的高速铁路建设中,不可避免的遇到各种复杂地质状况的隧道,浅埋软岩隧道就是其中一种。本文依托贵广高速铁路贺街隧道,进行了大量的现场试验,对采用6部CRD、二台阶、三台阶临时仰拱法施工的浅埋软岩隧道的地表沉降、地层分层沉降、初期支护的内力进行了现场监测,获取了大量实测数据,并结合FLAC3D取得了以下研究成果： (1)实测数据结果表明浅埋软岩隧道地表沉降经历前期变形阶段-加速变形阶段-趋于稳定阶段的历时过程,超前沉降比例和超前影响距离主要受到开挖跨度的影响；初期支护的及时闭合对软弱围岩变形的控制具有至关重要的作用；地层深部相对地表的沉降,经历前期变形阶段-加速变形阶段-缓慢抬升阶段-趋于稳定阶段的历时过程,其中缓慢“抬升”即意味着地层变形得到初步控制；文中还对比分析了不同超前加固措施对围岩变形的影响,结果表明地表旋喷桩加固后地表沉降减小55%,抗滑桩对控制偏压具有非常明显的作用,抗滑桩加固后地表沉降槽曲线较为对称。 (2)通过现场监测支护应力、应变,认为浅埋软岩隧道上覆地层自承载能力微弱,围岩压力表现为松散土压力,开挖初期初支-围岩接触压力增长迅速,部分断面在前期施工中压力就已经基本达到上覆全土柱自重；另外,下层围岩的开挖会引发“掉拱”,从而导致初支内力突变,对初支混凝土的破坏性较强。 (3)结合实测围岩变形与初支-围岩接触压力,得出实测拱顶沉降与接触压力之间的关系曲线,分析了采用不同施工方法时的围岩变形控制的合理范围。 (4)在变位分配原理的基础上,用FLAC3D模拟获得不同施工方法各施工步序的围岩变形的比例及控制值,结合实测资料,实现了对施工过程中拱顶沉降的控制,保证了二次衬砌的厚度,并对采用不同施工方法的不同施工段进行了拱顶预留量的优化分析,降低了施工成本。
[Abstract]:In the large-scale construction of high-speed railway, it is inevitable to encounter various kinds of tunnels with complicated geological conditions, among which the shallow soft rock tunnel is one of them. In this paper, a large number of field tests have been carried out based on the Hejie Tunnel of the Gui-Guang High Speed Railway. In this paper, the ground subsidence, stratified settlement and initial supporting internal force of shallow soft rock tunnel constructed by 6 CRD, two steps, three steps temporary invert method are monitored on the spot, and a large number of measured data are obtained. Combined with FLAC3D, the following research results have been obtained:. 1) the measured data show that the surface settlement of shallow soft rock tunnel goes through the process of early deformation, acceleration deformation and stabilization, and the advance settlement ratio and the advance influence distance are mainly affected by the excavation span. The timely closure of initial support plays an important role in controlling the deformation of soft surrounding rock, and the settlement of deep strata relative to the surface of the earth goes through the process of early deformation stage, acceleration deformation stage, slow uplift stage and stabilization stage. The slow "uplift" means that the deformation of the stratum is controlled preliminarily, and the influence of different advanced reinforcement measures on the deformation of surrounding rock is also compared and analyzed in this paper. The results show that the surface settlement is reduced by 55%, the anti-slide pile plays an obvious role in controlling the bias, and the surface settlement trough curve is more symmetrical after the reinforcement of the anti-slide pile. (2) through field monitoring of support stress and strain, it is considered that the self-bearing capacity of overlying stratum in shallow soft rock tunnel is weak, the surrounding rock pressure is expressed as loose soil pressure, and the initial branch and surrounding rock contact pressure increase rapidly in the early stage of excavation. In the early stage of construction, the pressure of some sections has basically reached the deadweight of the overburden whole earth column, in addition, the excavation of the surrounding rock of the lower layer will cause "arch drop", which will lead to the sudden change of the internal force of the initial support, which will be more destructive to the concrete of the initial support. 3) based on the measured deformation of surrounding rock and the contact pressure between initial branch and surrounding rock, the relation curve between measured settlement of arch roof and contact pressure is obtained, and the reasonable range of deformation control of surrounding rock under different construction methods is analyzed. 4) on the basis of the principle of displacement distribution, the proportion and control value of surrounding rock deformation of different construction methods are obtained by FLAC3D simulation. Combined with the measured data, the settlement of arch roof is controlled during construction. The thickness of the secondary lining is ensured, and the optimum analysis of the reserved amount of the arch roof is carried out for different construction sections with different construction methods, which reduces the construction cost.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U451

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